Here's my experience, seems to me very similar to most of you here, my MBP i5 mid 2010 ramdomly freezes, all I can move is the mouse, but nothing else works, only solution is to force shutdown, this usually happens more frequently at few seconds after booting and the desktop appears, but it also happens during normal operation, but not so often, especially when im with Twitter.app open.
And the other problem I am having lately is waking up from sleep, 40% of the times I try to wake it up from sleep everything turns on but the screen remains black, unninstalled everything I had and no go, it's the same (Running 10.7.3).
One thing that seems strange to me is, I mainly thought it was hardware problem, but then I installed 10.8 Developer Preview 2 (Just to test it) as my main OS (With 10.7 on the other partition), and with 10.8 DP2 the problem is gone! Believe me I tested it for more than 3 weeks of everyday use, so now I don't know what to think of this, the problem does not exist with 10.8, why it does on 10.7 with exactly the same programs installed?!
Normally I use GFX to force Intel Graphic Card, for better battery life, it does the same on "Dynamic Switching"
PS: I checked my logs, it has the "NVDA Channel Exception too, and when the freeze occurs it shows this:
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: 2012-04-09 12:33:48.238 com.apple.dock.extra[197:1707] Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: 2012-04-09 12:33:48.243 com.apple.dock.extra[197:1707] Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: 2012-04-09 12:33:48.255 com.apple.dock.extra[197:1707] Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: 2012-04-09 12:33:48.257 com.apple.dock.extra[197:1707] Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro com.apple.dock.extra[197]: Could not connect the action buttonPressed: to target of class NSApplication
Apr 9 12:33:48 MacBookPro coreservicesd[33]: *** process 33 exceeded 500 log message per second limit - remaining messages this second discarded ***